Multiple telegraph or telephone



2 Sheets-Sheet 1.

(No Model.)

A. M. ROSEBRUGH. MULTIPLE TELEGRAPH 0R TELEPHONE. No. 442,139.

Patented Dec. 9, 1890.

(No Model.) 2 Sheets-Sheet 2.

I A. M. ROSEBRUGH. MULTIPLE TELEGRAPH 0R TELEPHONE.

No. 442,139. 7 Patented Dec. 9, 1890.

w th moses gvwewfoc UNTTEn STATES PATENT OFFICE.

ABNER M. ROSEBRUGH, OF TORONTO, CANADA, ASSIGNOR TO THE AMERICA BELLTELEPHONE COMPANY, OF BOSTON, MASSACHUSETTS.

MULTlPLE TELEGRAPH OR TELEPHONE.

SPECIFICATION forming part of Letters Patent No. 442,139, dated December9, 1890.

Original application filed November 27, 1886, Serial No. 220,072.Divided and this application filed June 6, 1887. Serial No. 240,447. (Nomodel.) Patented in England August 15, 1885, No. 4,231.

To aZZ whom, it may concern.-

ie it known that I, ABNER MULHOLLAND ROSEBRUGH, surgeon, of the city ofToronto, county of York, Province of Ontario, Domin- 5 ion of Canada,have invented certain new and useful ln'iprovements in MultipleTelegraphs or Telephones, of which the following is a specification.

This invention was patented in Great Britain August 15, 1885, No.45,231.

The object of this invention is to increase the working capacity ofmetallic telephonecircuits, so that long-distance telephony may befacilitated, so that either two telephone- I subscribers or a telephonesubscriber and a telephone operator at each end of a metallic circuitmay communicate with each other simultaneously.

My present invention relates to the general subjectmattcr set forth inmy application Serial No. 220,072, filed Novembe' 27, 1880, and is adivision thereof; and it consists in the construction and arrangement ofdevices, substantially as hereinafter pointed out.

In the accompanying drawings, Figure 1 is a diagrammatic representationof an arrangement of circuits at one end of the line. Figs. 2 and aremodifications of the same. Fig. a is a diagrammatic representation ofthe arrangcment of circuits, showing the adjustable induction-coils, andFig. 5 is an enlarged detail showing one of the coils.

l and i? are the two wires of a metallic circuit at one of two centralstations, and K 5 is a branch line for grounding said metallic circuit.

R is a repeater arranged as a differential repeater.

D and F are two subscribers lines. Sub- 4o scriber F is represented asbeing connected with the duplex repeater and subscriber D with thebranch line K, while G and L represent the ordinary central-officetelephone switch.

I is a special switch for the branch line K, and J is a special switchfor the duplex repeater. The repeater is divided into two duplex orparts, one on each side of the branch line 1 ,thc wire 1) of one partbeing connected with wire 1, and the wire (1 on the other part beingconnected with wire The wires 1) and q, forming one side of therepeater, are continuous with the metallic circuit 1 and 2, while thewires 13 and q, forming the other side of the repeater, are connected atone 5 end with the ground-wire E and at the other end with the switch J.

The principle of a telephone-repeater is well known. A simple form isthat of an induction-coil with or without a soft-iron core, the primarybeing in one electric circuit and the secondary coil being in anindependent electric circuit, so that an impulse generated in onecircuit will affect the other circuit by induction.

In the duplex. repeater the subscribers line at each telephone-office isbrought within the inductive influence of both branches of the metalliccircuit 1 and 2 in such a manner that the induction into and from thetwo branches shall be equal. Any form of repeater may be used so long asthe inductive action between said repeater and the two branches of themetallic circuit and on each side of the branch line is equai and solong 7 5 as said repeater does not cause retardation of thetelephonecurrent either by high resist ance or by self-induction.

I preferably construct the d uplex repeater as follows: Referring toFig. 3, a cable with So two insulated wires is used, one wire 1) g be-.ing continuous with the metallic circuit and the other 1) q with thesubscribers line.

1 and 2 are the two wires of the metallic circuit connecting two centraloffices, each wire being continuous with one of the insulated wires ofthe repeating-cable. R is a re peater, and p q are the repeating-wirespassin g through the cables and being continuous with the metalliccircuit, while 1) q are the wires of the cable which connect with thesubscribers line. By this arrangement when the transmitter at D is usedthe current divides equally and passes into the two branches of themetallic circuit 1 and 2, and in so doing passes through the two sidesof the repeater, which it affects by induction, but in oppositedirections, and then one side neutralizes the other and the subscriberat F does not overhear what is being said. \Vhen the subscriber at F isto be placed in comm unication with another subscriber at the distantstation, the switches L and J are connected with such subscribers lineand the duplex repeater and the line-wires act as a metallic circuit, ashereinbefore explained, and repeat into the subscribers line at thedistant station, and when subscriber D communicates with the subscriberat the distant station the lines 1 and 2 act as a double conductor, andthus the two messages will not interfere with each other, as alreadyexplained. Hence the two subscribers at D and F may communicate with twosubscribers at the distant station by means of a metallic circuitwithout interference.

Fig. 4 shows substantially the same arrangement of circuits as is shownin Fig. 1 and havin g the same letters of reference, with the additionof indicating the adjustable inductioncoils.

Fig. 5 shows the adjustable induction-coils on a larger scale, thecircuits being lettered the same as in Fig. t. The deviceis providedwith a core 0, which slides through the coils, the two wires of whichare preferably wound side by side, and an adjusting-screw c, which isused to maintain the core in proper adjustment.

Having thus fully described my invention, what I claim is 1. Thecombination, in a system of telephonic communication, of a metallic ordouble parallel line-circuit extending between two or more stations,local circuits including telephone apparatus connected by means ofinduction-coils with both sides of the said double-line main circuit,and earth branches including telephones connected with the said metalliccircuits at the terminal stations thereof and at a point between thesaid inductioncoils, whereby the stations inductively connected with thedouble-line circuit may be enabled to communicate with one another, tothe exclusion of the earth-branch stations, and vice versa, ashereinbefore described.

' 2. In a system of telephonic communication, a metallic or doubleparallel line main circuit, a series of local circuits, each includingtelephones, and induction-coils, two for each local circuit, conn ectingthe said local circuits with both sides of the main circuit, one wire ofeach coil of a pair being included in the local circuit and theremaining wire of the two coils being interposed one in each line of themetallic circuit and earth-branch circuits, with telephones includedtherein united to the said metallic circuits at the terminal stationsthereof and ata point substantially equidistant from bothinductioncoils, substantially as and for the purposes hereinbeforedescribed.

3. The combination, substantially as hereinbefore described, of a mainmetallic or double-line circuit, a series of local circuits, eachincluding telephones and each connected by means of induction-coils withboth sides of the double-line circuit, earth branches connected with thesaid metallic circuit at the termini thereof and at a point thereofbetween the said induction-coils, and adjusting devices whereby theinductive power of the said coils may be varied, so that currentspassing between the earth branches may be accurately balanced in the twoinduction-coils and so that their effect upon the local-circuitreceiving-instruments maybe neutral.

at. The combination, in a system of telephone communication, of ametallic or double parallel line-circuit, earth branches includingtelephonic apparatus connected with the metallic circuit at bothtermini, a series of local circuits including telephones, and a pairofinduction-coils for each local circuit, whereby the said localcircuits are inductively connected with both sides of the metalliccircuit, as herein described, the said induction-coils having their twowires wound together, being of approximately equal resistance andinductive power, and being provided with adjustable cores, wherebycommunication may be individually maintained between the severallocal-circuit instruments and between the earth-branch instruments,substantially as set forth.

In testimony whereof I have signed my name to this specification in thepresence of two subscribing witnesses.

ABNER M. ROSEBRUGlT. \Yitnesses:

T. R. ROSEBRUGH, R. M. RosEBRucH.

